The conventional process for forming fiber reinforced plastic production boats or cultured marble vanities entails the application of a first layer inside of a female mold. The first layer of a fiber reinforced plastic boat is a gel coat which is partially cured to a condition in which the surfaces are still tacky. A fiber reinforced laminating resin is then layed up against the gel coat. Gel coats used in such processes are normally relatively thick, in the range of 0.5 to 0.8 mm, to provide protection against the environment and to hide the coarseness of the fiber reinforced main laminate.
Unsaturated polyester resins are widely used for marine and cultured marble gel coats because they are inexpensive, easy to work with and cure well at room temperature. Unsaturated polyester resins based on neopentyl glycol and isophthalic acid are currently the preferred materials for forming polyester gel coats because of their strength, flexibility, abrasion resistance and impact resistance. Nonetheless, such polyester resins are quite moisture permeable and provide less scratch and abrasion resistance than desirable. Therefore, other resins have been used for gel coats in an effort to overcome the aforementioned shortcomings. For example, vinyl ester gel coats are sometimes used when greater flexibility and resistance to water and chemicals are needed. However, vinyl esters require higher curing temperatures and are more expensive.
Epoxy resins have also been employed to give strong flexible and lighter weight composites with excellent water resistance properties. However, epoxies are as much as four times as expensive as polyesters and are much more difficult to work with and to cure. In U.S. Pat. No. 4,800,123 issued Jan. 24, 1989 and assigned to Freeman Chemical Corporation there is disclosed a method of coating urethane elastomers to provide such products as scratch resistant optically clear lenses such as those used for eye glasses. That disclosure did not, however, contemplate or address the problem of providing scratch resistant coatings on gel coated laminates such as those of the polyester type.
Various protective coatings have been applied over gel coated laminates after they have been cured in an effort to improve gloss retention as well as improved protection against water and chemical attack. Such coatings are generally applied to the cured laminate by conventional application techniques such as dipping, spinning, spraying, curtain and roller coating techniques. Coatings applied in this manner, however, usually require several hours of curing time and frequently demonstrate poor adhesion to the gel coat because of residual mold release materials on the gel coat surface. Although such mold release compositions can sometimes be removed by sanding or solvent wiping, the removal process involves further costly and time consuming processing steps in addition to altering and sometimes damaging the appearance of the surface.
The protective coating compositions currently available contain a high content of volatile organic materials, constituting environmental hazards, and often pose health risks to workers. Furthermore, such conventionally applied coatings often show surface imperfections such as orange peel effects, craters, runs, dust particles, and the like.
In the light of the foregoing continuing problems and various efforts to overcome them which have not been entirely satisfactory, a need exists for improved scratch resistant coatings and processes for forming such coatings.